Magnetic indicator



April 18, 1944. J. w. MCBRIDE EFAL MAGNETIC INDICATOR Filed June 7, 1941 wim EM N 3 m c I NMWMJMT wsF m -3 JMW B Patented Apr. 18, 1944 UNITED STATES PATENT OFFICE manure mmca'ron 'John w. McBride, Andrew 8.McB|-ide, and

Walton F. McBride, Burbank, Calif.

Application June 7,1941, Serial No. 391,142

v (01. 175-183) This invention relates to a magnetic indicator. 7

4Clalms.

More particularly, the invention relates to a system whereby it is possible to transfer accurately a pattern or design from one side of a non-magnetic member to the opposite side; without' the necessity of transferring measurements. Since such measurements obviously would require a transposition of the original pattern similar to the production of a mirror image, the possibilities of error under such circumstances are greatly multiplied. By the aid of the present invention, the pattern or design is very readily reproduced without the necessity of employing any measurements.

In assembling various structural parts made from sheet materiahfor example in airplane fuselages and wings, it is common practice to drill one of the members for the necessary attachment screws and bolts. The cooperating member to which the other member is to be attached may already be installed. To ensure proper alinement of the holes, the previously drilled member may be used as a pattern or template for drilling the other member. If there is enough room, the latter may be marked and drilled from the side to which the other member is attached. However, space limitations are frequently such as to require the member to be drilled from the opposite side. Thus, the location of the holes must be marked on this opposite side, and it is an object of this invention to provide means whereby this may be readily and accurately accomplished.

It is another object of this invention to provide such a device which is simple, compact and durable.

This invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of several embodiments of the invention. For.

this purpose there are shown a few forms in the drawing accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

In the drawing:

Figure 1 is a transverse section of the device showing it in use;

Fig. 2 is a cross section on an enlarged scale, as seen on plane 2-2 of Fig. 1;

1 Fig.d3 is a pictorial view of the device of Fig.

' Fig. 4 is a view similar to Fig. 1, showing a modified formof the invention.

Referring to Figs. 1, 2 and 3, a needle i of magnetic material, such as mild steel, is provided with a. pivotal support 2 in an appropriate support. such as a transparent tubular member 3 so as to extend generally longitudinally of the tube 3. The pivotal support 2, as clearly shown in Fig. 2, is of the type commonly known as gimbals" and includes a pair of pivots in perpendicular relationship. Thus an outer arcuate member 5 is suitably secured on the inside of tube 3. This member 5 pivotally supports a ring 6 by the aid of the radial pintles l. The needle I of magnetic material is in turn supported in ring ii by means of pintles 8 secured on needle i. The axis of pintles 8 is at a right angle with the axis of pintle i. In this way, the needle i is free to move in any direction about its support 2.

The lower end of tube 3 is open, and the needle i extends so that one end Iii is adjacent to the plane of this open end. The opposite end oi needle I is provided with a small counterweight ii, whereby the needle is balanced and has no tendency due to its weight to assume any particular position about its support 2.

It may be assumed that it is desired to locate the positions of holes to be drilled in a flat, non-magnetic member i3, and that these holes are to coincide with holes 2i on another nonmagnetic member 20. For this purpose member i3 is placed directly over member 20.

The device is used by placing a magnet, which may be a permanent magnet i2, at the point whose location it is desired to mark on the surface of a member iii. The device is then moved about in an exploratory manner over this surface, and as the point or pole center oi the magnetic field produced by magnet I2 is approached, the end Ill of needle I will be drawn toward it, so that the needle points toward the location of the point. When this occurs, slight exploratory movements of the tube 3 will not disturb the position of the end III, which nevertheless stays stationary even as tube 3 is moved about. Such a phenomenon thus serves eflectively to indicate that the needle i has found its pole represented by the tip of the point 22 of the magnet I2; thus this end ill of the needle sticks" to the point exactly opposite the tip of magnet II. The point to which the end It "sticks" may then be marked by a scriber or other suitable tool 14 inserted through a suitable opening l5 provided in the will of tube 3. Obviously, for the most accurate location of the point, the device-should be moved until the needle stands normal to the surface being marked, and to make such adjustment easier, the surface forming the lower end of the tube 3 is perpendicular to the axis of the tube.

The device is not limited to use on a plane surface, but by appropriate manipulation ma be used ,on any sort of curved surface. Further, although the device and its cooperating magnet I! are shown as alined on a vertical axis IE, it is not at all necessary that this axis be vertical; it can as well be horizontal or inclined at any angle.

For convenience to the operator, the device may be provided with a clip I! secured to a spring band l8 adapted to embrace tube 3. This clip l1l8 is similar to those used on fountain pens and pencils for securing them in pockets. By this means, the device may be easily secured in the operator's pocket when not needed where it will be handy and instantly available when wanted.

The pointed tip 22 of magnet I2 is adapted to enter the hole 2|. It gives an accurate indication of its position by producing a magnetic field which is concentrated at the center of the hole. To reduce the space requirements of the ma net the end portion 23 may be tapered.

In the modified form of Fig. 4, the needle I is supported for universal movement in tube 3 by a ball 25 secured on needle I and carried in a socket 26 secured in tube 3. Thus a ball-andsocket joint is formed. Opening 21 is for the same purpose as opening l5 but extends to th bottom of tube 3. An electro-magnet 28 i shown to create the magnetic field. It has a coil 29 arranged for energization from a suitable source 30 controlled by a switch 3|. Also, in this figure, the device is shown as cooperating to transfer the location of a point 32 from the lower sur-. face of the non-magnetic sheet member 33, to the opposite surface thereof. This point 32 'is previously determined; or it may be scribed or prick-punched in the lower surface of member 32.

What is claimed is:

1. In a device of the character described, a needle of magnetic material, an open ended tubular member, and a universal pivot structure carried by the tubular member for said needle and so arranged as to position the free end of the needle adjacent the open end of the tube.

2. In a device of the character described, a tubular member open at one end, a needle of magnetic material, and gimbals supporting said needle centrally in the tube, so that one end of the needle is adjacent the open end of the tube, the needle being substantially balanced about its support, there being an opening in the side of the tube adjacent the open end.

3. In a device of the character described, a needle of magnetic material, means for universally supporting said needle, and a support. for said means, said support having a contacting end defined by a surface transverse to the needle and soarranged that the free end of the needle lies near the said surface. I

4. In a device of the character described, a needle of magnetic material, means for universally supporting said needle, a support for said means, said support having a contacting end defined by a surface transverse to the needle and so arranged that the free end of the needle lies near the said surface, and means for producing a magnetic fleld transverse to said surface.

JOHN W. MCBRIDE. ANDREW S. MCBRIDE. WALTON F. MCBRIDE. 

